Foaming concentrates have been known and used since before 1940 for use as fire fighting agents, for crop protection and for a variety of other applications. Ingredients are added for a variety of reasons, for example: microbicides are often added to discourage bacterial decay of the foam, preservatives are added to impart shelf life stability, other ingredients are sometimes added to lower the freezing point, and/or to alter the viscosity.
For many applications it is desirable to produce a foam which is persistent for several days. Examples of such applications are as temporary covers for landfills and waste piles, covers for spills of hazardous materials and crop protection against frost. Because of this, a bactericide is usually added as a preservative to prevent the decomposition of the foam concentrate by bacteria. Protein hydrolysates are a constituent found in foam of a prior art formulation, as described in U.S. Pat. No. 5,225,095 to DiMaio, and also U.S. Pat. No. 5,133,991 to Norman et al. Because these hydrolysates are excellent nutrient sources for microbiological life forms, a low level toxicity biocide is usually recommended as an additive to preserve the concentrate. The fact that most foams are susceptible to microbial decomposition provides a basis for the conclusion that the art of fire-fighting foams teaches against the inclusion of microbial life forms in their formulations.
Organics-decomposing-microorganisms have been commercially available to clean oil spills from oil tankers and to assist in waste removal from grease interceptors in restaurants for some time now. Microbes specifically engineered for the decomposition of difficult organic compounds are well known and readily available. For example, Sybron Chemicals, Inc. manufactures the microbiological strains utilized in one embodiment of the present invention under U.S. Pat. Nos. 4,482,632 and 4,288,545, incorporated herein by reference. The microbiological strains of the Bacillus species particularly effective in the practice of the invention in connection with the consumption of volatile organic compounds are B. subtilis, B. licheniformis, and B. polymyxa.
In addition, the selection of one of the above strains is advantageous because these species of Bacillus are not true pathogens as are the species B. anthracis and B. cereus. Reports of infections in man caused by Bacillus species other than B. anthracis and B. cereus are rare. According to a report by the Department of Biology of the Virginia Polytechnic Institute and State University, B. subtilis, B. licheniformis, and B. polymyxa as described by the manufacturer, Sybron, would not constitute a public health hazard unless the microorganisms were used in an area where individuals with an unusual vulnerability (such as when undergoing an open-incision surgical procedure) would be exposed.
Investigation of microbial degradation of oil dates back to at least 1942, when the American Petroleum Institute began to subsidize research in the field. Considerable basic knowledge about factors that affect natural biodegradation, about the kinds of hydrocarbons capable of being degraded, and about the species and distribution of the microorganisms involved in biodegradation had already been developed in the early 1970s. For instance, the Office of Naval Research sponsored more than a dozen basic and applied research projects in the late 1960s and early 1970s on oil biodegradation to control marine oil spills. Since this time, a large number of refineries, tank farms, and transfer stations now employ in situ bioremediation to restore land contaminated by accidental spills of fuel oil or other hydrocarbons.
Probably the most important series of field tests of the use of fire-fighting foam to control organics and hydrocarbon fires were conducted in the aftermath of the Persian Gulf War. The oil field fires created an environment of urgency and necessity which focused creative minds on solving the problems at hand, and on concentrating on research and development to solve the problems which were anticipated to occur again in the future.
LIGHT WATER, Aqueous Film Forming Foam (a product of Minnesota Mining and Manufacturing) is the most commonly used fire-fighting aqueous film forming foam (AFFF) currently on the market. Despite this fact, it was rarely used during the oil field fires of Kuwait because of its relative ineffectiveness in extinguishing fires of such a magnitude and intensity (unless the source is completely blanketed with foam) and because of its relative inability to prevent flashbacks. In addition, LIGHT WATER and other brands of AFFF contain fluorinated surfactants and butyl-ether, both generally considered to be toxic substances. It has been observed that some soils contaminated with AFFF several years earlier still foam up during a rain for example. This is evidence of the persistence of the fluorosurfactant used and its resistance to biodegradation. This may present a hazard to fish and other forms of wildlife in shallow waters that breath through their pores, at least until the surfactant used in AFFF is sufficiently diluted or is naturally biodegraded. Being well aware of these negative side effects to AFFF's use, the United States Defense Department has been seeking a non-toxic yet effective alternative to AFFF.
Microorganisms (microbes) of the type used in the present invention are capable of assimilating and breaking down the non-soluble organic materials including hydrocarbons that compose grease and oil into relatively harmless substances of water-soluble products, carbon dioxide and a lesser quantity of fatty acids. These types of microorganisms are relatively commonplace in the environment.
The difficulty encountered in incorporating microbe cultures in a fire-fighting foam solution which will extinguish organically fueled fires and begin the disposal of the residual hydrocarbon waste products were many. The first challenge was the selection of a hardy strain of organics-consuming (primarily hydrocarbon-consuming) microorganisms which withstand the extremely severe environment associated with organically fueled fires in a proportion sufficient to adequately address the magnitude of the overall bioremediation challenge presented. A second challenge was determining the specific organism that digest or decompose a particular grease or oil and yet remain capable of being stabilized so that they have a satisfactory shelf life thereby being available when needed. A third challenge was the selection of a microbial strain which would stabilize in a surfactant strong enough to extinguish the fire. A fourth challenge was to control the microbe population so that they multiply and exist in sufficient quantities so as to accomplish the job of hydrocarbon waste removal in a timely fashion.
A need therefore exists for a bioremediating fire-fighting foam mixture and a method for the decomposition of organic materials which meets the challenges presented in order to reduce cleanup costs and increase the quality of the cleanup by providing an effective and environmentally safe means to do so.